IsOnWater_CSharp

What is it?

The purpose of the library is to check whether or not a coordinate point (Latitude, Longitude) is on water. It also provides a method to generate a random GeoPoint(double latitude, double longitude) with a OnWater boolean as a parameter.

Project structure

• OnWater: C# Library project.

  • OnWaterLib.cs: Main library which contains IsOnWater(GeoPoint p) and GenerateRandomGeoPoint(bool OnWater = false) methods.
  • Utilities.cs: utility classes such as PixelPoint, GeoPoint and some utility methods.
  • water_8k.png: 8k world water image used to check the point.

• OnWater.Tests: Console application used to test the library mentioned above.

How it works?

It follows these steps:

• Get GeoPoint (double latitude, double longitude) point.
• Convert it into PixelPoint(int X, int Y) point using CoordsToPixels(double latitude, double longitude) inside Utilities.cs.
• Check the (X, Y) pixel's color inside water_8k.png.
• If it is white the point is on water, otherwise it is on land.

private bool IsOnWater(PixelPoint p)
{
    Color color = Bmp.GetPixel(p.X, p.Y);
    if (color.Name == "ffffffff")
	return true;

    return false;
}

How it converts GeoPoint to PixelPoint

public static PixelPoint CoordsToPixels(double latitude, double longitude)
{
	var x = (longitude + 180) / 360 * 8192;
	var y = 4096 / 2 - latitude * 4096 / 180;
	return new PixelPoint((int)x, (int)y);
}

It is a simple proportion knowing that longitude goes from -180 to +180 and latitude goes from -90 to +90. You can get additional information about how latitude and longitude works following this link. 8192 and 4096 are water_8k.png dimensions.

Changelog

• 02 March 2019: First release